[rescue] Serial console - break "filtering" connection - resistor method
Brandon Applegate
vom513 at gmail.com
Mon Oct 16 23:23:56 EDT 2023
So the NUD4273… From:
https://www.usenix.org/events/lisa00/full_papers/drzyzgula/drzyzgula.ps
—-
It contains fifteen resistors, eight diodes, three transistors, one op amp and five capacitors – one of them a large 1000uF electrolytic.
—-
Finally found a picture:
https://web.archive.org/web/20010614020819/http://www.nudata.com/pdf/4273_Sellsheet.pdf
Man I’d love to be able to clone that.
Sent from my phone
> On Oct 16, 2023, at 6:50 PM, vom513 <vom513 at gmail.com> wrote:
>
> Hello all,
>
> So I have a couple of dumb terminals (the one I’m using to test now is a WYSE-160). I’m using an IPX as the test machine. So this has the DIN-8 to DB25 cable.
>
> As we all know, by default, when dropping the console connection (i.e. turning the terminal off) - Suns will drop to PROM/debugger :(
>
> Years ago there was supposedly a pricey cable/dongle (NuData 4273) that would “shield” the Sun from break signals. Another hardware solution I’ve seen mention of is putting a resistor in the connection to disable break signals. This is the rabbit hole I’m going down.
>
> I’m trying to use this:
>
> https://hea-www.cfa.harvard.edu/~fine/Tech/cs1.2/Sun-serial
>
> According to that, we are pulling -5v off pin 25, running it through a 4.7k resistor, and connecting this to pin 3 on the Sun side ? Am I reading that correctly ?
>
> On my IPX - I seem to get nothing off pin 25 (testing with DMM, and tried the shield as well as pin 7 as ground).
>
> I do however seem to get -5v off pin 1. If I’m reading that Harvard URL right - I should be able to use pin 1 in place of 25 ? I’m leery of this as I’d really rather not blow up the serial port and/or machine itself…
>
> So any info anyone can give me on this would be greatly appreciated. I’d really like to be able to power my dumb terminal off/on as well as use a serial switchbox without dropping the box(es) to PROM.
>
> Thanks.
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